Master station and method for high-efficiency wi-fi (hew) communication with a minimum ofdma bandwidth unit

ABSTRACT

Embodiments of a master station and method for communicating in a Wi-Fi network in accordance with a high-efficiency Wi-Fi (HEW) technique are generally described herein. In some embodiments, the master station is configured to communicate with scheduled stations using the antennas within a bandwidth comprising one or more 20 MHz Wi-Fi channels using a plurality of minimum orthogonal frequency division multiple access (OFDMA) bandwidth units during an OFDMA control period during which the master station has exclusive control of a wireless medium. Each minimum OFDMA bandwidth unit may comprise a predetermined number of subcarriers that do not include guard subcarriers of the channel wherein the guard subcarriers are provided at band edges of the bandwidth, the guard subcarriers being in addition to the subcarriers of each of the minimum OFDMA bandwidth units. In some embodiments, no guard subcarriers are provided between the minimum OFDMA bandwidth units within a 20 MHz channel.

PRIORITY CLAIMS

This application claims the benefit of priority under 35 U.S.C. 119(e) to:

Ser. No. 61/906,059 filed Nov. 19, 2013 [4884.031PRV (P62429Z)],

Ser. No. 61/973,376 filed Apr. 1, 2014 [4884.078PRV (P65247Z)],

Ser. No. 61/976,951 filed Apr. 8, 2014 [4884.087PRV (P65769Z)],

Ser. No. 61/986,256 filed Apr. 30, 2014 [4884.103PRV (P66983Z)],

Ser. No. 61/986,250 filed Apr. 30, 2014 [4884.104PRV (P66984Z)],

Ser. No. 61/991,730 filed May 12, 2014 [4884.108PRV (P67789Z)],

Ser. No. 62/013,869 filed Jun. 18, 2014 [4884.120PRV (P69557Z)], and

Ser. No. 62/024,801 filed Jul. 15, 2014 [4884.128PRV (P70599Z)]

which are all incorporated herein by reference in their entireties.

TECHNICAL FIELD

Embodiments pertain to wireless networks. Some embodiments relate to wireless local area networks (WLANs), Wi-Fi networks and networks operating in accordance with one of the IEEE 802.11 standards, such as the IEEE 802.11ac standard or the IEEE 802.11ax SIG (named DensiFi). Some embodiments relate to high-efficiency wireless or high-efficiency WLAN (HEW) communications.

BACKGROUND

Wi-Fi communications has been evolving toward ever increasing data rates (e.g., from IEEE 802.11a/g to IEEE 802.11n to IEEE 802.11ac). The upcoming IEEE 802.11ax Task Group for HEW is the next evolution of these standards. HEW is intended to provide an increase in data capacity while maintaining compatibility with legacy systems. There are general needs for achieving an increase in data capacity while maintaining compatibility with legacy systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an HEW network in accordance with some embodiments;

FIG. 2 illustrates a subcarrier configuration of a 20 MHz channel configured with 5 MHz subchannels;

FIG. 3 illustrates a subcarrier configuration for 20 MHz, 40 MHz, 80 MHz and 160 MHz channels;

FIG. 4 illustrates a 20 MHz channel configured with OFDMA minimum bandwidth unit subchannels in accordance with some embodiments;

FIG. 5 illustrates a wideband channel configured with OFDMA minimum bandwidth unit subchannels in accordance with some embodiments; and

FIG. 6 illustrates an HEW communication device in accordance with some embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

FIG. 1 illustrates an HEW network in accordance with some embodiments. HEW network 100 may include a master station (STA) 102, a plurality of HEW stations 104 (i.e., HEW devices) and a plurality of legacy stations 106 (legacy devices). The master station 102 may be arranged to communicate with the HEW stations 104 and the legacy stations 106 in accordance with one or more of the IEEE 802.11 standards. In some embodiments, the master station 102 may be arranged to communicate with the HEW stations 104 in accordance with an IEEE 802.11ax standard for HEW. In some embodiments, the master station 102 may be an access point (AP), although the scope of the embodiments is not limited in this respect.

In accordance with embodiments, the master station 102 may include physical layer (PHY) and medium-access control layer (MAC) circuitry which may be arranged to contend for a wireless medium (e.g., during a contention period) to receive exclusive control of the medium for an HEW control period (i.e., a transmission opportunity (TXOP)). The master station 102 may transmit an HEW master-sync transmission at the beginning of the HEW control period. During the HEW control period, the HEW stations 104 may communicate with the master station 102 in accordance with a non-contention based scheduled multiple-access technique. This is unlike conventional Wi-Fi communications in which devices communicate in accordance with a contention-based communication technique, rather than a non-contention multiple-access technique. During the HEW control period, legacy stations 106 refrain from communicating. In some embodiments, the master-sync transmission may be referred to as an HEW control and schedule transmission.

In accordance with embodiments, the master-sync transmission may include a multi-device HEW preamble arranged to signal and identify data fields for a plurality of scheduled HEW stations 104. The master station 102 may further be arranged to transmit (in the downlink direction) and/or receive (in the uplink direction) one or more of the data fields to/from the scheduled HEW stations 104 during the HEW control period. In these embodiments, the master station 102 may include training fields in the multi-device HEW preamble to allow each of the scheduled HEW stations 104 to perform synchronization and an initial channel estimation.

In accordance with some embodiments, an HEW station 104 may be a Wi-Fi or IEEE 802.11 configured station (STA) that is further configured for HEW operation (e.g., in accordance with IEEE 802.11ax). An HEW station 104 may be configured to communicate with a master station 102 in accordance with a non-contention-based multiple access technique, such as a scheduled orthogonal frequency division multiple access (OFDMA) technique, during the HEW control period and may be configured to receive and decode the multi-device HEW preamble of an HEW frame. An HEW station 104 may also be configured to decode an indicated data field received by the master station 102 during the HEW control period.

In accordance with some embodiments, the master station 102 may be configured to communicate with scheduled stations 104 within a bandwidth comprising one or more channels using a plurality of minimum OFDMA bandwidth units during an OFDMA control period during which the master station 102 has exclusive control of a wireless medium. In these embodiments, each minimum OFDMA bandwidth unit comprises a predetermined number of subcarriers that do not include guard subcarriers of the channel. In these embodiments, the guard subcarriers are provided at the band edges of the bandwidth and the guard subcarriers are in addition to the subcarriers of each of the minimum OFDMA bandwidth units. In these embodiments, no guard subcarriers need to be provided between the minimum OFDMA bandwidth units of a channel. These embodiments are discussed in more detail below.

The embodiments disclosed herein provide an OFDMA design for HEW that is backward compatible and can coexist with legacy Wi-Fi. These embodiments use to as large of an extent as possible the legacy channelization. These embodiments provide a minimum OFDMA bandwidth unit that aligns well with the legacy OFDM structure. Aside from the new novel OFDMA allocation that is discussed in more detail below, embodiments disclosed herein further afford coexistence with the legacy IEEE 802.11 standards including the legacy IEEE 802.11ac standard. The High Efficiency WLAN Study Group (HEW SG) (now IEEE 802.11ax Task Group) has been starting to evolve Wi-Fi from the 802.11ac/ah proposed standards. This study group has, as one of the target use cases, high density deployment scenarios such as stadiums, hotspots and also cellular offloading. A main use case in this new group is for dense deployments and cellular offloading. The minimum OFDMA bandwidth unit allocation disclosed herein provides symmetrical sub-channelization and may improve the overall system spectrum utilization, thereby improving the overall system efficiency, particularly in these target use case scenarios.

Since one main use case in HEW is dense deployments with many devices trying to access the medium with moderate data rates, methods which allow more simultaneous access may be needed. The current IEEE 802.11ac specification allows for up to 160 MHz of bandwidth with eight simultaneous MIMO streams. The focus for HEW is to use that fat pipe (wide bandwidth) to provide access to many devices using OFDMA. In accordance with some embodiments, a minimum ODFMA bandwidth unit is defined that aligns with legacy channelization. Previous to 802.11 HEW, OFDMA was not used as an access mechanism in Wi-Fi. Embodiments disclosed herein attempt to reuse as much as possible the basic physical layer blocks utilized for implementing the previous releases of the IEEE 802.11 Wi-Fi standards.

In accordance with embodiments, the minimum OFDMA bandwidth unit is configured to allow an efficient and extendable OFDMA configuration. In some embodiments, a minimum bandwidth size of 4.375 MHz is provided. In these embodiments, the allocation of bandwidth may be done in a manner that also allows it to be backwards compatible with legacy devices in that the waveform for the disclosed sub-channels will allow the CCA detection in the middle of the OFDMA transmissions for legacy devices (e.g., symbol times may be aligned). Thus a protection mechanism is provided, making this approach far more attractive that other approaches.

As of this date, these other approaches do not address asymmetry in the band edge where guard tones are provided to avoid adjacent interference and to limit spectral mask. Embodiments that define a minimum OFDMA bandwidth unit for subchannelization disclosed herein are more efficient and provide a symmetrical allocation of spectrum, as well as provide for alignment with 11n/ac channelization and backward compatibility with legacy systems.

FIG. 2 illustrates a subcarrier configuration of a 20 MHz channel configured with 5 MHz subchannels. As illustrated in FIG. 2, the total number of subcarriers is 56 of which 52 are data subcarriers and 4 are pilots. For a 20 MHz channel, the pilot subcarriers may be located at positions −21, −7, 7, and 21 with respect to the DC subcarrier at the center of the band. As shown, there is a null at the four guard subcarriers 204 (on the left) and a null at the three guard subcarriers 204 (on the right) to provide guard bands. These guard bands are used for legacy communications to limit the interference level to adjacent channels and to provide enough margin to account for power-amplifier backoff and filtering. As depicted in FIG. 2, dividing the 20 MHz channel into 5 MHz bandwidth allocations 202 causes asymmetry because the usable bandwidth at either edge is smaller than the middle bands (i.e., not all subcarriers of each 5 MHz allocation can used).

FIG. 3 illustrates a subcarrier configuration for 20 MHz, 40 MHz, 80 MHz and 160 MHz channels. As illustrated in FIG. 3, there may be a similar asymmetry in 40, 80 and 160 MHz channels as described with respect to the 5 MHz allocations of FIG. 2. For the 40 MHz, 80 MHz and 160 MHz channels, the guard bands are may be wider (e.g., with 6 and 5 subcarrier allocation on each edge).

FIG. 4 illustrates a 20 MHz channel configured with OFDMA minimum bandwidth unit subchannels in accordance with some embodiments. To avoid the asymmetry described with respect to FIGS. 2 and 3, embodiments disclosed herein define an OFDMA bandwidth unit 402 based on the number of subcarriers in each unit. In some embodiments, the minimum OFDMA bandwidth unit may be 14 subcarriers which, in some embodiments, may equal to 14×312.5 KHz=4.375 MHz, using the same FFT size as defined in a legacy system. In particular, to enable legacy coexistence, the same FFT size may be used and hence the symbol duration and guard interval will allow the CCA detection during any part of the OFDMA transmissions for legacy devices 106 (FIG. 1). This allows legacy devices 106, if they wake-up during the OFDMA transmission to perform guard interval detection and defer transmission using the same mechanism as outlined in the legacy specification. Thus, legacy devices 106 would correctly defer achieving legacy coexistence.

In some embodiments, if it is decided to increase FFT size and thereby a change in symbol duration and guard interval (e.g., to support outdoor channels) the number of subcarriers of an OFDMA bandwidth unit may be increased with the same ratio as the FFT size is increased while the minimum bandwidth allocation of 4.375 MHZ may remain constant. For example, if the FFT size is increased to an 128-point FFT from the legacy 64-point FFT for 20 MHz operation, there may be 14×128/64=28 subcarriers with a reduced subcarrier spacing of 20 MHz/128=156.25 KHz resulting with the a minimum OFDMA unit of 28×subcarrier spacing=4.375 MHz.

Table 1 in below summarizes the number of OFDMA sub-channels and subcarriers design in each 20, 40, 80 and 160 MHz operational mode in accordance with some embodiments. As described in more detail below, the number of OFDMA sub-channels in increased to 17 and 36 for 80 MHz and 160 MHz, respectively (in contrast with 16 and 32 (respectively for 80 and 160 MHz) for an asymmetrical sub-channel allocation when 5 MHz is used as the smallest OFDMA unit). Thus, embodiments disclosed herein provide a symmetrical OFDMA structure with a minimum OFDMA unit that allows simultaneous access for more users and hence better utilization of the spectrum.

TABLE 1 BW of Max Number of Total Data &Pilot + Extra null Operation Subchannels DC + Guard subcarriers 20 MHz 4  56 + 1 + 7 — 40 MHz 8 112 + 1 + 7  8 80 MHz 17 238 + 1 + 7 10 80 + 80 MHZ 34 238 + 1 + 7 for each 20 160 MHz 36 504 + 1 + 7 —

In accordance with embodiments, mapping of a modulation and coding scheme (MCS) in each OFDMA sub-channel is simplified since the OFDMA bandwidth units disclosed here are symmetrical. The asymmetrical structure as shown for example in FIGS. 2 and 3 may require different MCS mapping in sub-channels on either edge vs. the sub-channels in the middle of the band because they would utilize different number of subcarriers.

In accordance with embodiments, the master station 102 may be configured to communicate with scheduled stations 104 within a bandwidth 401 comprising one or more channels using a plurality of minimum OFDMA bandwidth units 402 during the OFDMA control period during which the master station 102 has exclusive control of a wireless medium. Each minimum OFDMA bandwidth unit 402 may comprise a predetermined number of subcarriers that do not include guard subcarriers of the channel. In these embodiments, the guard subcarriers are provided at band edges 404 of the bandwidth 401. The guard subcarriers may be in addition to the subcarriers of each of the minimum OFDMA bandwidth units 402, and no guard subcarriers need to be provided between the minimum OFDMA bandwidth units 402 of a channel.

In some embodiments, the extra null subcarriers identified in Table 1 may be used as guard subcarriers and may be provided in between the minimum OFDMA bandwidth unit, although the scope of the embodiments is not limited in this respect. These embodiments would relax the requirement on frequency accuracy of each user that is assigned to a minimum OFDMA bandwidth unit as frequency inaccuracy can cause inter-carrier interference. ICI).

In some embodiments, for processing signals of a 20 MHz channel with a 64-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit 402 is fourteen (14) with a subcarrier spacing of 312.5 KHz, and each minimum OFDMA bandwidth unit 402 occupies a bandwidth of 4.375 MHz. In these embodiments, the master station 102 may communicate with scheduled stations 104 using a plurality of 4.375 MHz subchannels, wherein each 4.375 MHz subchannel corresponds to a minimum OFDMA bandwidth unit 402.

In these embodiments, a subcarrier spacing that is consistent with legacy IEEE 802.11 systems (e.g., 312.5 KHz) may be used. The use of fourteen data subcarriers for a minimum OFDMA bandwidth unit 402 provides a symmetric bandwidth allocation since no guard subcarriers are included. This is unlike the 5 MHz bandwidth allocations 202 illustrated in FIG. 2 which are asymmetric allocations since the 5 MHz bandwidth allocations 202A and 202D at the band edges 204 would need to include guard subcarriers (which would not be used). As a result, the 5 MHz bandwidth allocations 202A and 202D would utilize fewer subcarriers than the 5 MHz bandwidth allocations 202B and 202C near the center of the channel. Thus the 5 MHz bandwidth allocations 202A and 202D at the band edges 204 may have a lower data handling capacity (as well as a lower MCS) than the 5 MHz bandwidth allocations 202B and 202C near the center of the channel. This asymmetry may result in increased implementation complexity, among other disadvantages. In accordance with these embodiments, symmetry is provided by the minimum OFDMA bandwidth units 402 since they use the same predetermined number of subcarriers and none of the subcarriers are guard subcarriers.

FIG. 5 illustrates a wideband channel configured with OFDMA minimum bandwidth unit subchannels in accordance with some embodiments. In these embodiments, the master station 102 (FIG. 1) may be configured to communicate with scheduled stations 104 within a bandwidth 501 comprising one or more channels using a plurality of minimum OFDMA bandwidth units 402 during an OFDMA control period during which the master station 102 has exclusive control of a wireless medium. Each minimum OFDMA bandwidth unit 402 comprises a predetermined number of subcarriers that do not include guard subcarriers of the channel. In these embodiments, each channel of the wideband channel may be a 20 MHz channel, and when the channel is a wideband channel 501 and comprises two or more adjacent 20 MHz channels, no guard subcarriers are provided between at least some of the adjacent minimum OFDMA bandwidth units 402 of the two or more adjacent 20 MHz channels although the scope of the embodiments is not limited in this respect. In some other embodiments, guard subcarriers may be provided between each adjacent 20 MHz channel at the band edges 404 (FIG. 4).

Some alternate embodiments may use different FFT sizes and may provide smaller minimum OFDMA bandwidth units. For example, for processing with a 20 MHz channel with a 256-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit 402 may be fourteen. In these embodiments, each minimum OFDMA bandwidth unit may occupy a bandwidth of 1.09375 MHz. In these embodiments, sixteen minimum OFDMA bandwidth units may occupy a 20 MHz channel rather than the four illustrated in FIG. 4. In these embodiments that use larger FFT sizes (e.g., 128, 256 or 512 for a 20 MHz channel), the subcarriers may occupy a smaller bandwidth (i.e., the bandwidth may be scaled down by the ratio of FFT sizes (i.e., 128/64 for a 128-point FFT, 256/64 for a 256-point FFT and 512/64 for a 512-point FFT). For example, for a 256-point FFT, the subcarriers may occupy 4.375/(256/64)=1.09375 MHz. Different FFT sizes may also be used for wideband channels.

In some embodiments, larger minimum OFDMA bandwidth units may be provided. For example, for processing signals of a 20 MHz channel with a 64-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit is twenty-eight (28) with a subcarrier spacing of 312.5 KHz. In these embodiments, each minimum OFDMA bandwidth unit may occupy a bandwidth of 8.75 MHz. In these embodiments, two minimum OFDMA bandwidth units may occupy a 20 MHz channel rather than the four illustrated in FIG. 4.

In some embodiments, for processing signals of a 20 MHz channel with a 128-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit may be twenty-eight (28) with a subcarrier spacing of 156.25 KHz. In these embodiments, each minimum OFDMA bandwidth unit may occupy a bandwidth of 4.375 MHz. In these example embodiments, four minimum OFDMA bandwidth units of 28 subcarriers each may occupy a 20 MHz channel. These embodiments may, for example, be used to support outdoor channels, although the scope of the embodiments is not limited in this respect.

In some embodiments, each channel may be a 20 MHz channel comprising four minimum OFDMA bandwidth units 402 and the channel utilized by the master station 102 for communicating with the scheduled stations 104 during the OFDMA control period comprises one or more adjacent 20 MHz channels. In some embodiments, for communicating with scheduled stations 104 during the OFDMA control period using a channel comprising a single 20 MHz channel (i.e., having a 20 MHz bandwidth), the single 20 MHz channel may provide four minimum OFDMA bandwidth units 402 for a total of 56 data subcarriers, in addition to a DC subcarrier and 7 guard subcarriers at the band edges 404 (see table 1). In the example illustrated in FIG. 4, one band edge may have three guard subcarriers while the other band edge may have four guard subcarriers. In the example illustrated in FIG. 4, no guard subcarriers are provided between the minimum OFDMA bandwidth units 402 of a channel.

In some embodiments, for communicating with scheduled stations 104 during the OFDMA control period using a wideband channel comprising two or more adjacent 20 MHz channels (e.g., for bandwidths of 40 MHz, 80 MHz and, 160 MHz), the master station 102 may allocate the minimum OFDMA bandwidth units 402 of the two or more adjacent 20 MHz channels without guard subcarriers therebetween although the scope of the embodiments is not limited in this respect as guard subcarriers may be provided between each 20 MHz channel at the band edges 404. In some of these embodiments, no guard subcarriers may need to be provided between the minimum OFDMA bandwidth units 402 of the two or more adjacent 20 MHz channels due the spectral alignment inherent in OFDMA communications (i.e., the OFDMA signals may be aligned in power, frequency and time). This is unlike legacy IEEE 802.11 communications within each 20 MHz channel. In these embodiments, the subcarriers of adjacent channels that were previously guard subcarriers may be used for communicating data.

In some embodiments, for communicating with scheduled stations 104 during the OFDMA control period using a wideband bandwidth 501 (e.g., a wideband channel) comprising two contiguous or adjacent 20 MHz channels for a bandwidth of 40 MHz, the master station 102 may allocate up to eight minimum OFDMA bandwidth units 402 of fourteen (14) subcarriers each for a total of 112 data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges 504 (see table 1). These embodiments may use a 64-point FFT. When 256-point FFT is used, number of allocations may at least scale up with a ratio of 256/64. In the example illustrated in FIG. 5, one band edge of the wideband bandwidth 501 may have three guard subcarriers while the other band edge may have four guard subcarriers. In these 40 MHz embodiments, there may be several (e.g., eight) extra or null subcarriers that may go unused when no guard subcarriers are provided in-between the adjacent 20 MHz channels of the 40 MHz wideband channel. In some embodiments, the extra or null subcarriers may be used as guard subcarriers in between minimum OFDMA bandwidth units to relax hardware implementations such as local oscillator accuracy in each user device.

In some embodiments, extra null subcarrier may be added to the guard subcarriers at both band edges of 40 MHz, assigned between the two 20 MHz sub-channels, assigned between minimum OFDMA units, and/or assigned around DC (e.g., to ease requirement on DC offset).

In some embodiments, for communicating with scheduled stations 104 during the OFDMA control period using a wideband channel comprising four contiguous 20 MHz channels for a bandwidth of 80 MHz, the master station 102 may allocate up to seventeen (17) minimum OFDMA bandwidth units of fourteen (14) subcarriers each for a total of up to 238 data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges 504 (see table 1). These embodiments may use a 64-point FFT. When 256-point FFT is used, number of allocations may at least scale up with a ratio of 256/64. In these 80 MHz embodiments that provide up to 17 minimum OFDMA bandwidth units 502, there may be several (e.g., ten) extra or null subcarriers that may go unused when no guard subcarriers are provided in-between the adjacent 20 MHz channels of the 80 MHz wideband channel. In some embodiments, the extra or null subcarriers may be used as guard subcarriers in between minimum OFDMA bandwidth units. In these 80 MHz embodiments, by eliminating the guard subcarriers between the adjacent 20 MHz channels, an additional minimum OFDMA bandwidth unit can be allocated (i.e., 17 minimum OFDMA bandwidth units of 14 subcarriers each instead of 16). Note that eliminating 7 guard subcarriers between each 20 MHz would result in 3×7=21 extra null subcarriers. An 80 MHz channel has 6 and 5 guards on each band edges instead of 4 and 3 for 20 MHz, and has 3 nulls at & around DC. The change of the structure of these nulls may provide an additional minimum OFDMA unit plus the extra nulls as stated in Table 1.

In some embodiments, for communicating with scheduled stations 104 during the OFDMA control period using a wideband channel comprising a bandwidth of eight contiguous 20 MHz channels for a bandwidth of 160 MHz, the master station 102 may allocate up to thirty-six (36) minimum OFDMA bandwidth units of fourteen (14) subcarriers each for a total of up to 504 data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges 504. These embodiments may use a 64-point FFT. When a 256-point FFT is used, number of allocations may at least scale up with a ratio of 256/64. In these 160 MHz embodiments, most or all of the guard subcarriers would conventionally have been provided in-between the adjacent 20 MHz channels can be used for communications. In these 160 MHz embodiments, by eliminating the guard subcarriers between the adjacent 20 MHz channels, several (e.g., up to four) additional minimum OFDMA bandwidth unit can be allocated (i.e., up to 36 minimum OFDMA bandwidth units of 14 subcarriers each instead of 32.)

In some embodiments, the master station 102 may be configured for communicating with scheduled stations 104 during the OFDMA control period using a wideband channel comprising two non-contiguous 80 MHz wideband channels (i.e., an 80+80 MHz channel) for a bandwidth of 160 MHz. For each 80 MHz wideband channel of the 80+80 MHz channel, the master station 102 may allocate up to seventeen (17) minimum OFDMA bandwidth units of fourteen (14) subcarriers each for a total of up to 238 data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges 504. In these embodiments that use a wideband channel having a bandwidth of 160 MHz comprising two non-contiguous 80 MHz wideband channels (i.e., an 80+80 bandwidth channel) each 80 MHz channel may comprise four contiguous 20 MHz channels. In these embodiments, null subcarriers may be assigned on band edges of each 80 MHz channel. Therefore less than the 36 allocations of the 160 MHz contiguous bandwidth channel can be allocated. For example, the subcarriers of at least one of the 36 allocations may be spared for guard bands and null subcarriers. In some embodiments that utilize a 160 MHz bandwidth, thirty five (35) minimum OFDMA bandwidth units may be used and the extra null subcarriers (that could be used for another minimum OFDMA bandwidth unit) may be used for null subcarriers in between the minimum OFDMA bandwidth unit.

In some embodiments, the master station may allocate bandwidth to the scheduled stations 104 based on the minimum OFDMA bandwidth unit 402 for communication with the master station during the control period. The scheduled stations 104 may be high-efficiency wireless (HEW) stations 104 (i.e., IEEE 802.11ax) and the master station 102 may be an access point configured for HEW communications with the HEW stations 104 and configured for legacy communications with legacy stations 106 (e.g., IEEE 802.11ac). In these embodiments, during the OFDMA control period, the master station 102 may communicate with the scheduled HEW stations 104 in accordance with a non-contention-based multiple access technique, such as a scheduled OFDMA and/or spatial-division multiple access (SDMA) techniques, using the minimum OFDMA bandwidth units. Outside the OFDMA control period, the master station may be configured to communicate with stations, including legacy stations 106, in accordance with a contention based communication technique (conventional IEEE 802.11, CSMA/CA).

In some embodiments, the minimum OFDMA bandwidth units 402 are configurable to be time and frequency multiplexed within the control period. During the control period, packets may be received from the scheduled stations 104 in accordance with an uplink SDMA technique using OFDMA, or packets may be transmitted to the scheduled stations 104 in accordance with a downlink multiplexing technique using OFDMA. In some embodiments, during the control period, packets may be received from the scheduled stations 104 in accordance with an uplink SDMA technique using OFDMA, although the scope of the embodiments is not limited in this respect.

In some embodiments, the master station 102 may transmit, during an initial portion of the control period, a master-sync transmission that includes a multi-device preamble arranged to signal and identify data fields for the plurality of scheduled stations 104. The master-sync transmission may identify parameters of the minimum OFDMA bandwidth units 402 for use by the scheduled stations 104 for communicating with the master station 102 during the control period. Communications during the control period use the minimum OFDMA bandwidth unit 402. In some embodiments, scheduled stations 104 may be allocated more than one minimum OFDMA bandwidth unit 402, as the minimum OFDMA bandwidth unit 402 is the minimum amount of bandwidth that may be allocated.

In some of these embodiments, a little extra power-amplifier (PA) back-off and filtering may help define the guard band consistently across all bandwidths to be 1250 KHz (4 null subcarriers on the left and 3 on the right) on band edges 404 (FIG. 4) and 504 (FIG. 5). In some alternate embodiments, extra null subcarriers may be allocated to provide extra guard band to be similar to the legacy allocation shown in FIG. 3. Some embodiments may use only 16 out of the 17 possible (or 35 out of 36) sub-channels for a 80 MHz channel or only 35 of the 36 possible sub-channels for a 160 MHz channel, to free up one OFDMA unit for use as 14 extra null subcarriers. The availability of extra null subcarriers in 40, 80 and 160 MHz wideband channels can provide flexibility in the design. As mentioned earlier, the extra null subcarriers may either be allocated as guard or can be allocated around DC to relax requirements on DC offset cancellation. The extra null subcarriers may also be allocated in between OFDMA units to relax requirements on oscillator accuracy.

FIG. 6 illustrates an HEW communication device in accordance with some embodiments. HEW device 600 may be an HEW compliant device that may be arranged to communicate with one or more other HEW devices, such as HEW stations 104 (FIG. 1) or master station 102 (FIG. 1), as well as communicate with legacy devices. HEW device 600 may be suitable for operating as master station 102 (FIG. 1) or an HEW station 104 (FIG. 1). In accordance with embodiments, HEW device 600 may include, among other things, hardware processing circuitry that may include physical layer (PHY) circuitry 602 and medium-access control layer circuitry (MAC) 604. PHY 602 and MAC 604 may be HEW compliant layers and may also be compliant with one or more legacy IEEE 802.11 standards. PHY 602 may be arranged to transmit HEW frames, such as HEW frame (FIG. 4). HEW device 600 may also include other processing circuitry 606 and memory 608 configured to perform the various operations described herein.

In accordance with some embodiments, the MAC 604 may be arranged to contend for a wireless medium during a contention period to receive control of the medium for the HEW control period and configure an HEW frame. The PHY 602 may be arranged to transmit the HEW frame as discussed above. The PHY 602 may also be arranged to receive an HEW frame from HEW stations. MAC 604 may also be arranged to perform transmitting and receiving operations through the PHY 602. The PHY 602 may include circuitry for modulation/demodulation, upconversion/downconversion, filtering, amplification, etc. In some embodiments, the processing circuitry 606 may include one or more processors. In some embodiments, two or more antennas may be coupled to the physical layer circuitry arranged for sending and receiving signals including transmission of the HEW frame. The memory 608 may be store information for configuring the processing circuitry 606 to perform operations for configuring and transmitting HEW frames and performing the various operations described herein.

In some embodiments, the HEW device 600 may be configured to communicate using OFDM communication signals over a multicarrier communication channel. In some embodiments, HEW device 600 may be configured to receive signals in accordance with specific communication standards, such as the Institute of Electrical and Electronics Engineers (IEEE) standards including IEEE 802.11-2012, 802.11n-2009 and/or 802.11ac-2013 standards and/or proposed specifications for WLANs including proposed HEW standards, although the scope of the invention is not limited in this respect as they may also be suitable to transmit and/or receive communications in accordance with other techniques and standards. In some other embodiments, HEW device 600 may be configured to receive signals that were transmitted using one or more other modulation techniques such as spread spectrum modulation (e.g., direct sequence code division multiple access (DS-CDMA) and/or frequency hopping code division multiple access (FH-CDMA)), time-division multiplexing (TDM) modulation, and/or frequency-division multiplexing (FDM) modulation, although the scope of the embodiments is not limited in this respect.

In some embodiments, HEW device 600 may be part of a portable wireless communication device, such as a personal digital assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone or smartphone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or other device that may receive and/or transmit information wirelessly. In some embodiments, HEW device 600 may include one or more of a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

The antennas of HEW device 600 may comprise one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas or other types of antennas suitable for transmission of RF signals. In some multiple-input multiple-output (MIMO) embodiments, the antennas may be effectively separated to take advantage of spatial diversity and the different channel characteristics that may result between each of antennas and the antennas of a transmitting station.

Although HEW device 600 is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including digital signal processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), radio-frequency integrated circuits (RFICs) and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, the functional elements of HEW device 600 may refer to one or more processes operating on one or more processing elements.

Embodiments may be implemented in one or a combination of hardware, firmware and software. Embodiments may also be implemented as instructions stored on a computer-readable storage device, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage device may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage device may include read-only memory (ROM), random-access memory (RAM), magnetic disk storage media, optical storage media, flash-memory devices, and other storage devices and media. Some embodiments may include one or more processors and may be configured with instructions stored on a computer-readable storage device.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b) requiring an abstract that will allow the reader to ascertain the nature and gist of the technical disclosure. It is submitted with the understanding that it will not be used to limit or interpret the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment. 

What is claimed is:
 1. A master station comprising hardware processing circuitry including physical-layer circuitry and medium-access control layer circuitry and configured to communicate in a Wi-Fi network, the hardware processing circuitry configured to: communicate with scheduled stations within a bandwidth comprising one or more channels using a plurality of minimum orthogonal frequency division multiple access (OFDMA) bandwidth units during an OFDMA control period during which the master station has exclusive control of a wireless medium, wherein each minimum OFDMA bandwidth unit comprises a predetermined number of subcarriers that do not include guard subcarriers of the channel.
 2. The master station of claim 1 wherein the guard subcarriers are provided at band edges of the bandwidth, the guard subcarriers being in addition to the subcarriers of each of the minimum OFDMA bandwidth units, and wherein no guard subcarriers are provided between the minimum OFDMA bandwidth units of a channel.
 3. The master station of claim 1 wherein each channel is a 20 MHz channel, and wherein when the channel is a wideband channel and comprises two or more adjacent 20 MHz channels, no guard subcarriers are provided between adjacent minimum OFDMA bandwidth units of the two or more adjacent 20 MHz channels.
 4. The master station of claim 3 wherein for processing signals of a 20 MHz channel with a 64-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit is fourteen (14) with a subcarrier spacing of 312.5 KHz, and wherein each minimum OFDMA bandwidth unit occupies a bandwidth of 4.375 MHz.
 5. The master station of claim 3, wherein for processing with a 20 MHz channel with a 256-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit is fourteen (14), and wherein each minimum OFDMA bandwidth unit occupies a bandwidth of 1.09375 MHz.
 6. The master station of claim 4 wherein each channel is a 20 MHz channel comprising four minimum OFDMA bandwidth units, wherein the channel utilized by the master station for communicating with the scheduled stations during the OFDMA control period comprises one or more adjacent 20 MHz channels, wherein for communicating with scheduled stations during the OFDMA control period using a channel comprising a single 20 MHz channel, the single 20 MHz channel is configured to provide four minimum OFDMA bandwidth units for a total of 56 data subcarriers, in addition to a DC subcarrier and seven (7) guard subcarriers at the band edges.
 7. The master station of claim 6 wherein for communicating with scheduled stations during the OFDMA control period using a wideband channel comprising two or more adjacent 20 MHz channels, the master station is configured to allocate the minimum OFDMA bandwidth units of the two or more adjacent 20 MHz channels without guard subcarriers therebetween.
 8. The master station of claim 7 wherein for communicating with scheduled stations during the OFDMA control period using a wideband bandwidth comprising two contiguous 20 MHz channels for a bandwidth of 40 MHz, the master station is configured to allocate up to eight minimum OFDMA bandwidth units of fourteen (14) subcarriers each for a total of 112 data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges.
 9. The master station of claim 8 wherein for communicating with scheduled stations during the OFDMA control period using a wideband channel comprising four contiguous 20 MHz channels for a bandwidth of 80 MHz, the master station is configured to allocate up to seventeen (17) minimum OFDMA bandwidth units of fourteen (14) subcarriers each for a total of up to 238 data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges.
 10. The master station of claim 9 wherein for communicating with scheduled stations during the OFDMA control period using a wideband channel comprising a bandwidth of eight contiguous 20 MHz channels for a bandwidth of 160 MHz, the master station is configured to allocate up to thirty-six (36) minimum OFDMA bandwidth units of fourteen (14) subcarriers each for a total of up to data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges.
 11. The master station of claim 9 wherein for communicating with scheduled stations during the OFDMA control period using a wideband channel comprising two non-contiguous 80 MHz wideband channels for a bandwidth of 160 MHz, wherein for each 80 MHz wideband channel, the master station is configured to allocate up to seventeen (17) minimum OFDMA bandwidth units of fourteen (14) subcarriers each for a total of up to 238 data and pilot subcarriers, a DC subcarrier and seven (7) guard subcarriers at the band edges.
 12. The master station of claim 2 wherein the master station is configured to allocate bandwidth to the scheduled stations based on the minimum OFDMA bandwidth unit for communication with the master station during the control period, wherein the scheduled stations are high-efficiency wireless (HEW) stations and the master station is an access point configured for HEW communications with the HEW stations and configured for legacy communications with legacy stations, wherein the minimum OFDMA bandwidth units are configurable to be time and frequency multiplexed within the control period, and wherein during the control period: packets are received from the scheduled stations in accordance with an uplink SDMA technique using OFDMA, or packets are transmitted to the scheduled stations in accordance with downlink multiplexing technique using OFDMA, wherein the master station is further configured to: transmit, during an initial portion of the control period, a master-sync transmission that includes a multi-device preamble arranged to signal and identify data fields for the plurality of scheduled stations, wherein the master-sync transmission identifies parameters of the minimum OFDMA bandwidth units for use by the scheduled stations for communicating with the master station during the control period, and wherein communications during the control period use the minimum OFDMA bandwidth unit.
 13. The master station of claim 1 wherein the guard subcarriers are provided at band edges of the bandwidth, the guard subcarriers being in addition to the subcarriers of each of the minimum OFDMA bandwidth units, and wherein extra subcarriers are provided between the minimum OFDMA bandwidth units of a channel.
 14. A method for communicating in a Wi-Fi network performed by a master station, the method comprising: communicating with scheduled stations within a bandwidth comprising one or more channels using a plurality of minimum orthogonal frequency division multiple access (OFDMA) bandwidth units during an OFDMA control period during which the master station has exclusive control of a wireless medium, wherein each minimum OFDMA bandwidth unit comprises a predetermined number of subcarriers that do not include guard subcarriers of the channel.
 15. The method of claim 14 wherein the guard subcarriers are provided at band edges of the bandwidth, the guard subcarriers being in addition to the subcarriers of each of the minimum OFDMA bandwidth units, and wherein no guard subcarriers are provided between the minimum OFDMA bandwidth units of a channel.
 16. The method of claim 14 wherein each channel is a 20 MHz channel, and wherein when the channel is a wideband channel and comprises two or more adjacent 20 MHz channels, no guard subcarriers are provided between adjacent minimum OFDMA bandwidth units of the two or more adjacent 20 MHz channels.
 17. The method of claim 16 wherein for processing signals of a 20 MHz channel with a 64-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit is fourteen (14) with a subcarrier spacing of 312.5 KHz, and wherein each minimum OFDMA bandwidth unit occupies a bandwidth of 4.375 MHz.
 18. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors to perform operations for communicating in a Wi-Fi network performed by a master station, the operations to configure the master station to: communicate with scheduled stations within a bandwidth comprising one or more channels using a plurality of minimum orthogonal frequency division multiple access (OFDMA) bandwidth units during an OFDMA control period during which the master station has exclusive control of a wireless medium, wherein each minimum OFDMA bandwidth unit comprises a predetermined number of subcarriers that do not include guard subcarriers of the channel.
 19. The non-transitory computer-readable storage medium of claim 18 wherein the guard subcarriers are provided at band edges of the bandwidth, the guard subcarriers being in addition to the subcarriers of each of the minimum OFDMA bandwidth units, and wherein no guard subcarriers are provided between the minimum OFDMA bandwidth units within a 20 MHz channel.
 20. The non-transitory computer-readable storage medium of claim 19 wherein for processing signals of a 20 MHz channel with a 64-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit is fourteen (14) with a subcarrier spacing of 312.5 KHz, and wherein each minimum OFDMA bandwidth unit occupies a bandwidth of 4.375 MHz.
 21. A master station comprising: one or more radios; a memory; physical-layer circuitry and medium-access control layer circuitry and configured for communicating in a Wi-Fi network in accordance with a high-efficiency Wi-Fi (HEW) technique, the circuitry configured to: communicate with scheduled stations using the antennas within a bandwidth comprising one or more 20 MHz Wi-Fi channels using a plurality of minimum orthogonal frequency division multiple access (OFDMA) bandwidth units during an OFDMA control period during which the master station has exclusive control of a wireless medium, wherein each minimum OFDMA bandwidth unit comprises a predetermined number of subcarriers that do not include guard subcarriers of the channel wherein the guard subcarriers are provided at band edges of the bandwidth, the guard subcarriers being in addition to the subcarriers of each of the minimum OFDMA bandwidth units, wherein no guard subcarriers are provided between the minimum OFDMA bandwidth units within a 20 MHz channel, wherein for processing signals of each 20 MHz channel with a 64-point FFT, the predetermined number of data and pilot subcarriers for each minimum OFDMA bandwidth unit is fourteen (14) with a subcarrier spacing of 312.5 KHz, and wherein each minimum OFDMA bandwidth unit occupies a bandwidth of 4.375 MHz.
 22. The master station of claim 21 wherein for communicating with scheduled stations during the OFDMA control period using a wideband channel comprising two or more adjacent 20 MHz channels, the master station is configured to allocate the minimum OFDMA bandwidth units of the two or more adjacent 20 MHz channels without guard subcarriers therebetween.
 23. The master station of claim 22 further comprising one or more antennas coupled to the one or more radios. 